Open angle glaucoma, a disease that affects 1-2% of the population, is characterized by excessive elevation of intraocular fluid pressure in the eye. The ciliary epithelium is the site at which the formation of aqueous humor fluid in the eye is regulated. Calcium is thought to have a central role in mediating multiple cell functions including secretion and the transport of fluids and electrolytes in many cells. One of the mainstays of glaucoma treatment is the use of drugs that decrease the secretion of aqueous humor fluid form the ciliary epithelium. Unfortunately, many currently available drugs that decrease aqueous humor production may cause serious side effects such as cardiac arrhythmias and arrest, pulmonary dysfunction, and CNS side effects such as decreased libido and depression (Zimmerman et al., 1983; Gardner, 1988). The investigation of calcium metabolism and phosphatidylinositol hydrolysis in ciliary epithelial cells will lead to a greater understanding of their secretory function and regulation by hormones and drugs. We propose to study the effects of drugs, hormones, and neurotransmitters on the mobilization of intracellular and extracellular calcium stores, and the subsequent elevation of cytosolic free calcium, in nonpigmented and pigmented ciliary epithelial cells grown in culture. The measurements of the inositol phosphates that mediate these effects will aid our understanding of the regulation of cell function which underlies stimulus-secretion coupling in these cells. The identity of the G protein(s) that couple receptors to their prominent effector systems, adenylate cyclase and phospholipase C, will be sought using quantitative immunological techniques in conjunction with specific antibodies to G protein subunits. Pertussis toxin- catalyzed ADP ribosylation of the alpha-subunits of G proteins coupled to phosphatidylinositol hydrolysis will be used to assist in the identification and characterization of these G proteins. Ultimately, these studies will provide new insights into the cell biology of ciliary epithelium and may lead to therapeutic alternatives for glaucoma therapy that are safer and more efficacious than those currently in use.